This invention relates to a data base system having a buffer memory section which memorizes selected ones of data blocks transferred from a data base section.
A data base system of the type described comprises data base section for memorizing a plurality of data blocks to be searched, a processing section, and a buffer memory section between the data base section and the processing section. The buffer memory section is for temporarily memorizing selected ones of the data blocks as buffered data blocks. In addition, the processing section comprises a processing unit operable in accordance with a plurality of processing programs. At any rate, each of the processing programs runs on the processing unit.
Let a specific one of the data blocks be searched by a specific one of the processing programs through the processing unit to be received by the specific processing program. In this event, the specific processing program produces a request data block search signal which specifies the specific data block so that the processing unit accesses the data base section to deliver the specific data block to the buffer memory section. After delivery of the specific data block to the buffer memory section, the specific data block is often renewed into a renewal data block by the processing unit. The processing unit makes a data base history file store the specific data block as a history data. Furthermore, the processing unit sends the renewal data block to the buffer memory section and thereafter to the data base section on renewal of the specific data block into the renewal data block.
Under the circumstances, it is assumed that a fault occurs in the data base system during a search operation of the specific data block. In this case, the specific data block should be restored because an error might be included in the specific data block. Specifically, the processing unit accesses the data base history file to read the history data from the data base history file and sends the history data to the data base section in order to restore the specific data block in the data base section.
However, it is difficult to quickly restore the specific data block in the data base section in the conventional data base system because the history data must be read from the data base history file before transfer of the specific data block to the data base section. In addition, a processing ability of the processing unit is lowered because the processing unit inevitably refers to the data history file during each restoring operation.